1. Field of the Invention
The present invention generally relates to a flapper valve that may be used to hydraulically isolate a portion of a wellbore tubular, the flapper valve being made of a frangible material that may be broken with a hydraulic impact sleeve. The flapper is movable from an open position and a closed position and may be biased to the closed position. The flapper is comprised of a frangible material, such as ceramic, that is adapted to shatter upon impact by an impact sleeve. The pressure within the tubular above the closed flapper may encourage the flapper to shatter once a crack is made in the flapper valve by the impact sleeve.
The impact sleeve may be used to initially hold open the flapper valve allowing fluid flow through the wellbore tubular. When it is desired to hydraulically isolate a portion of the wellbore tubular, the impact sleeve may be moved up the wellbore tubular to a second position allowing the flapper valve to close. A latching mechanism may be used to selectively retain the impact sleeve at the second position. For example, the impact sleeve may be connected to a collet located within the wellbore tubular. A mandrel may be inserted within the collet and may be used to raise the collet and the sleeve up the tubular to the second position. In the second position, the sleeve may be located adjacent a piston that is releasably connected to the wellbore tubular. A shearable device, such as a shear screw, may be used to releasably connect the piston to the tubular. The shearable device permits the release of the piston when the pressure within the tubular is increased to a predetermined amount.
After using the mandrel to move the sleeve to the second position, the collet may be deformed to release the mandrel. The piston may be used to hold the collet and/or the impact sleeve at the second position until it is desired to break the frangible flapper valve. The pressure within the tubular may be increased to the amount required to shear the shearable device, thus releasing the piston. The elevated pressure within the wellbore drives the piston and thus, the impact sleeve downwards towards the closed flapper valve. The impact of the sleeve against the flapper valve causes the flapper valve to shatter within the wellbore tubular. The lower end of the impact sleeve may be adapted to promote the shattering of the frangible flapper valve. Further, the lower end of the impact sleeve may be adapted to impact the frangible flapper valve about its outer edge. A second latching mechanism may be used to retain the piston and/or impact sleeve at a position within the wellbore after the frangible flapper valve has been shattered.
2. Description of the Related Art
There are a various number of sealing elements and/or valves that have been used in the oil and gas industry to isolate a portion of a wellbore tubular. Flapper valves are often a preferred sealing means because flapper type valves generally require less radial space than other commercially available valves and/or sealing means. Flapper valves are generally biased, by a spring or other resilient member, to close and hydraulically isolate a portion of the tubular when the flapper is not being held open. Prior to being closed, a mandrel or sleeve is often inserted through the flapper valve to hold open the valve. The mandrel or sleeve is then removed when it is necessary to isolate a portion of the wellbore below the flapper valve.
The closed flapper may cause a high pressure differential to be created on the opposite sides of the closed flapper making it difficult to reopen. Further, it may be difficult to grab a hold of the flapper with a tool to reopen the valve. Other flapper valves have been designed to be operated hydraulically, which increases the complexity of the valve. In order to overcome the difficulties of opening a closed flapper valve, a number of prior flapper valves have been designed to break under an elevated pressure within the wellbore tubular. These type flapper valves must be designed to hold an amount of pressure to adequately isolate a portion of the wellbore tubular, but to shatter or break upon the application of an elevated amount of pressure. However, it is difficult to predict when and at what pressure such a flapper will break.
In light of the foregoing, it would be desirable to provide flapper valve that is designed to be shattered by the impact of a sleeve within the wellbore tubular. It would further be desirable to provide a means for releasing the sleeve at a predetermined pressure within the wellbore tubular. The use of a shearable device, such as a shear pin, provides an accurate prediction of when the sleeve will be released within the wellbore shattering the flapper valve. It would be desirable to provide a flapper valve comprised of a frangible material to promote the shattering of the valve upon impact from the sleeve.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.